As illustrated in example FIG. 1, a semiconductor metal line may include gate dielectric layer 12 and poly gate 14 formed on and/or over semiconductor substrate 10, and spacer 16 formed on sidewalls of gate dielectric layer 12 and poly gate 14. First interlayer dielectric 18 is formed on and/or over the entire surface of substrate 10 including poly gate 14 and spacer 16. Lower contact plug 20, composed of a metal such as tungsten (W), is formed in first interlayer dielectric 18 to connect source/drains and gates to lower metal line M1 formed on and/or over first interlayer dielectric 18. Lower metal line M1 may include lower layer 22, aluminum (Al) metal layer 24 and upper layer 26. Upper contact plug 30, upper metal line M2 and second interlayer dielectric 28 are structured in a similar manner to lower contact plug 20, lower metal line M1 and first interlayer dielectric 18, respectively.
More specifically, in order to construct lower metal line M1 and upper metal line M2, lower layer 22, metal layer 24 and upper layer 26 are sequentially deposited on and/or over first interlayer dielectric 18 and second interlayer dielectric 28, respectively. Next, lower layer 22, metal layer 24 and upper layer 26 are partially etched such that a plurality of lower metal lines M1 and upper metal lines M2 are formed spaced apart from one another as illustrated in FIG. 1. Generally, the same etching gas is used when etching upper layer 26, metal layer 24 and lower layer 22. Since metal layer 24 is etched prior to lower layer 22, lateral sides of metal layer 24, being exposed, are attacked during etching of lower layer 22. More particularly, in a case where aluminum (Al) is used for the metal line, intervals between the metal lines are reduced as the size of the semiconductor device is reduced. Therefore, when etching lower layer 22 formed of titanium (Ti) or titanium nitride (TiN) by reactive ion etching (RIE), fluorine contained in CxFy gas used for etching lower layer 22 may affect sidewalls of Al layer 24 which is already etched. Accordingly, the reliability of the device, especially electromigration (EM), may be deteriorated.